Details:

Abstract

Taste changes are frequently reported by patients undergoing cancer treatment. Taste problems are difficult to assess and treat in the clinical oncology setting. This two-part study aimed to determine the use of terminology in the verbal and written assessment and treatment of taste problems in oncology patients. Two research methods were utilised: a retrospective audit of dietitians’ medical note entries (n=200) for 30 patients with head and neck cancer and; a qualitative interview study of oncology clinicians (n=23). The word ‘taste’ was used by the researcher as a generic term for taste and flavour. Clinicians use the word ‘taste’ when referring to issues concerning the wider pheonema of flavour and food hedonics. Dietitians documented the presence of taste or flavour problems in 73% of patients, but did not distinguish between taste and flavour. Specific management strategies were documented in only 23% of patients, indicating a disconnect between symptomatology and clinical management. Oncology clinicians report that patients use a total of 34 terms to describe taste and flavour problems, whereas oncology clinicians themselves use a total of 13 terms. Oncology clinicians identified gaps in current knowledge of predictors and classification of taste or flavour problems and in evidence-based supportive strategies to best manage these problems. For taste or flavour problems associated with cancer and its treatment to be effectively treated, the problem must first be accurately classified. A taxonomy of taste, flavour and food hedonics for application in the clinical setting is needed.

Taste is one of the five senses and refers to the perception derived when chemical molecules stimulate receptors in the areas of the tongue, soft palate and oropharyngeal region of the oral cavity.1 The taste system plays a role in food selection and in a biological sense is subserved by five basic taste qualities: sweet, salty, sour, bitter and umami (savoury).1 These taste qualities allow humans to identify safe and nutritious foods appropriate for metabolic needs, or serve as a warning system for harmful foods, thereby increasing the chance of survival. The sense of taste also contributes to the pleasure or enjoyment experienced as part of eating and drinking (hedonics). The ability to perceive taste sensations guides food choice, which in itself is a determinant of health.2

Although the words ‘taste’ and ‘flavour’ have specific and distinct meanings in the sensory science literature,3 they are often used interchangeably by patients and clinicians.4The perception of flavour includes the sense of taste together with the senses of smell and touch. Flavour also includes inputs from temperature of food and drink or oral pain sensations (for example chili burn).5 Any problems with these sensory or hedonic elements of flavour can affect the enjoyment of food.

Cancer treatment can affect taste via several proposed physiological and psychological routes, including: an alteration in the number of normal taste cells; interruption in neural transmission of signals from taste receptors to the taste processing centre in the brain;5 secretion of chemotherapy drugs into saliva; and learned food aversions as a result of negative association between nausea inducing chemotherapy and certain foods.6 This can manifest in: altered sensitivity to specific taste qualities (eg. sweet, salty); foods tasting different from usual; a bitter taste or metallic sensation in the mouth; or the rejection of particular foods as aversive to the patient.7

In addition to a possible influence on the chemical sense of taste, cancer and its treatment is known to affect the senses of smell and touch, as well as cognition and hedonic experience of food and drink. Hedonic experience refers to a psychological determination of the extent to which eating and drinking is pleasurable.8 Food hedonics encompass food liking and appetite. These effects are associated with reduced food enjoyment, altered nutritional status and quality of life due to: reduced energy and nutrient intake;9weight loss;3,10,11 impaired or altered desire to procure food; diminished food appreciation;12 changed patterns of food intake and rituals and social activities linked to eating and drinking;13,14and emotional distress and interference with daily life.15-17 Disorders of taste are generally difficult to diagnose and treat, often because of a lack of routine assessment practices, as well as limited knowledge and understanding of this sense and its disease states.10Whether, or to what extent, changes to taste function play a role in reduced food enjoyment among people receiving chemotherapy is unknown. It is hypothesised however, as a result of a recently conducted systematic review,18that problems with food liking and appetite occur independently of taste in people receiving chemotherapy. Additionally, the language of taste and flavour is important. Patient descriptions of how they experience particular sensations may provide the key to diagnosis of specific problems and can even suggest the course of therapy.19 For example, a constant unpleasant oral sensation such as a “metallic taste” in the mouth may warrant different treatment to an increase in the perceived intensity of sweetness expressed as “food tastes really sweet”. The use of agreed terminology is fundamental to standardising words used to name a patient’s health problems or needs, and to enable clear descriptions of terms used by researchers.20 It is not until a clinical problem is adequately identified and described that it can start to be monitored and managed.

The objective of this study was to determine whether and how taste or flavour problems are discussed with patients in the clinical oncology setting and to explore the needs of the cancer clinicians to better manage these symptoms.

Methods

Part A: Dietitian’s documentation auditA retrospective audit of dietitians’ medical note entries for 30 patients with head and neck cancer receiving nutritional care during the time period January to August 2008 was conducted at Peter MacCallum Cancer Centre in Melbourne. The sampled documentation pertained to patients chronologically registered for treatment within the head and neck unit who were under the care of a dietitian. The hard copy medical history for each of these patients was examined by the researcher to isolate entries made by a dietitian during the study period. From each dietetic entry (n=200), the following data was extracted: whether taste or flavour problems were documented; the terms used by dietitians to document such problems; and any specific strategies documented to address the problems listed. Data was analysed using descriptive statistics and frequency counts.

Part B: Oncology clinician qualitative interview studyPurposive sampling was utilised to recruit oncology nurses (n=6), medical oncologists (n=6) and oncology dietitians (n=11) with different levels of experience (table 1) from two health care facilities to participate in face to face interviews. A semi-structured interview framework developed by an oncology dietitian and oncology nurse researcher was used as a basis to explore clinician practice. Two issues investigated during interview are reported in this publication:

The language used by clinicians and patients to describe taste or flavour related problems. To investigate this issue, clinicians were asked: “What words do you actually use when you discuss taste? What words do patients use?” In this context, ‘taste’ was used by the researcher to determine if taste was being used as a defacto term for taste and flavour by clinicians. Interview data was analysed using content analysis based on a modified version of Melzack and Torgerson’s language of pain framework.19 In adapting this framework for relevance to taste and flavour, consideration was given to the sensory and hedonic elements associated with taste and flavour perception in humans. Categories and subcategories for patient and clinician descriptors of taste and flavour were identified. Reported terms and phrases were assigned to these categories.

The needs of oncology clinicians to better manage taste or flavour problems. To investigate this issue, clinicians were asked: “If there was one thing you had at your disposal which helped patients with taste problems, what would it be?” Responses were categorised into themes identified by two independent researchers.

For each issue investigated, data items were highlighted and coded. Coded data items were then collated and sorted into potential categories in tabular form. Appropriateness of categories was discussed and refined in consultation with the supervising researcher (an oncology nurse), resulting in redefinition and collapse of some categories. Repeat categorisation of all coded data items were then conducted blindly by two authors, resulting in 83% agreement after the first pass. Assignment of data items into categories were then compared and discussed among all authors. This process resulted in agreement of further sub-categorisation and re-assignment of data items until consensus for categorisation of each data item was attained.

Ethical approval to conduct these studies and publish the results was granted by the Ethics Committees of Peter MacCallum Cancer Centre and Eastern Health.

Results

Part A: Dietitian’s documentation auditThe documentation of 10 dietitians across 30 patients was examined in this audit. A total of 89 of the 200 medical entries included some documentation of taste or flavour problems, made by nine dietitians. This represented 73% (22 of 30) of patients whose notes were audited. In total, 13 different terms were used by dietitians to describe taste and flavour problems in this head and neck cancer patient group (table 2). Only six of the 89 medical note entries which referred to taste or flavour clearly referred to the sense of taste (one of the five basic tastes). It was unclear whether the remaining entries referred to taste or other elements of flavour of food hedonics (sense of smell or touch, liking, appetite or cognitive processing), despite all but one phrase containing the word ‘taste’. Management strategies addressing taste or flavour problems were documented by four different dietitians on six occasions for five patients. Overall, while taste or flavour problems were documented for 73% of patients, only 23% also had documented plans for management of the problem. The wording of the documented strategies was non-specific (table 3).

Part B: Oncology clinician qualitative interview studyTerms used by oncology clinicians and patients to describe the qualities and dimensions of taste and flavour problems fell into three distinct categories (sensory, hedonic and intensity). ‘Sensory’ refers to the human senses and ‘hedonics’ refers pleasure and displeasure. ‘Intensity’ may refer to sensory or hedonic properties. These categories were further broken down into seven sub-categories (sensory-taste, sensory-smell, sensory-touch, hedonic-wanting, hedonic-liking, hedonic-preference, intensity). Table 4 shows the assignment of reported terms to these categories and gives further detail of category definitions. Clinicians reported 34 terms used by patients and 13 terms used by clinicians to describe taste or flavour problems. Only three terms referred to true taste function and the remainder referred to elements of flavour (32), appetite (2) or food liking (10). The most common terms reported to be used by patients were “metallic”, “cardboard” and “no taste”. The range of terms used by clinicians was more limited than patients. There were many commonalities in terms used by clinicians and patients, but dietitians and doctors tended to also use more technical terms (such as ’dysgeusia’), which are reportedly reserved for discussion among clinicians rather than by clinicians with patients.

In coding clinicians’ responses to the question of what is needed to better manage taste problems experienced by their patients, the central themes of ‘evidence’ and ‘information’ were identified. Evidence referred to reliable and credible scientific data required to inform practice. Information referred to practical and credible resource material which could be given to patients. Clinician responses pertaining to evidence and information were categorised in three main ways (characterising, supportive strategies and therapeutic devices). Table 5 shows the assignment of participant responses to these categories by the profession and gives further detail of category definitions. One of these categories (characterising) was further broken down into three sub-categories, characterising-assessment – (does the problem exist), characterising-diagnostic tool (measurement techniques to determine which patients will experience what symptoms) and characterising-predictors (who is at risk of a particular problem).

Clinicians often specified the type of supportive strategy they were seeking, which included referral pathways, symptom relief, improved nutrition and food enjoyment. Nurses and dietitians (half of each group) most frequently identified supportive strategies which related to symptom relief, improved nutrition or enhanced food enjoyment to better support patients with taste or flavour problems. Supportive strategies identified by medical oncologists were linked to referral pathways (dietitian referral) rather than to symptom relief, improved nutrition or enhanced food enjoyment. Medical oncologists were more likely to identify therapeutic devices (50% of medical oncologist participant group) on their ‘wish list’ than were nurses (33%) or dietitians (27%). Therapeutic devices included a mouth spray or mouthwash (table 5).

Discussion

From the dietitians’ documentation audit, it was clear that taste and flavour related complications in patients are frequently identified by this group of professionals, but with little or no distinction between the various aspects of flavour that might be affected by cancer therapies. Specific management strategies to address the identified problems were not observed. The qualitative interviews with oncology clinicians revealed that problems with taste, flavour or hedonics are currently all classified as ‘taste problems’. Taste and flavour complications include: changes to the sense of smell or touch (texture); reduced or heightened taste sensitivity; food aversions; offensive or phantom sensations (metallic); or the flavour of food perceived differently to what it previously did or resembling some other item or object. Additionally, food may taste the same but that taste is no longer pleasant.7Both the audit and the interviews demonstrated that dietitians and other clinicians have limited capacity to distinguish between these differing side-effects of treatment.

Some clinicians cited a lack of evidence-based practice as a reason that discussing (and therefore treating) taste and flavour problems with their patients was difficult. Oncology clinicians report that strategies to manage taste and flavour problems are less concrete, or lack evidence, compared to strategies used to manage other toxicities of cancer treatment. For example, evidence-based clinical practice guidelines exist for mucositis and nausea and vomiting.21, 22 Routine methods of assessing taste and flavour related complications are not employed in the clinical oncology setting and no clinical guidelines exist for the management of problems with taste or flavour.

Regardless of whether problems pertain to taste, flavour or food hedonics, the end result for patients is likely to be decreased food enjoyment, which has implications for nutritional, gastronomical and social domains of life quality. Further research is now needed to develop a taxonomy of taste, flavour and food hedonics, which may give clinicians better diagnostic clues to the precise nature of these problems and inform the design and testing of interventions to ameliorate specific symptoms.